Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensing panels, and the like. Touch sensing panels, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. A touch sensor panel can be a panel with a touch-sensitive surface. The touch sensor panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Alternatively, the touch sensor panel can be a standalone input device such as a touch pad on a laptop. Touch sensor panels can allow a user to make various touch or hovering inputs via one or more touch objects such as fingers or styli. In general, the touch sensor panel can recognize the touch and position of one or more touches thereon, and the computing system can interpret the touch and thereafter perform an action based on the touch event.
A typical touch sensor panel typically includes a number of touch nodes. For example, in a capacitive touch sensor panel, each touch node can be formed by a capacitive coupling between a drive line and a sense line. A touch image can be captured from the touch sensor panel based on the capacitive readings from the touch nodes of the panel. The touch image can reflect, for example, the locations of one or more touches on the touch sensor panel.
One type of touch sensor panels can be implemented as an array of nodes formed by multiple drive lines crossing over multiple sense lines, where the drive and sense lines are separated by a dielectric material. This type of touch sensor panels is referred to as Double-layer Indium Tin Oxide (DITO) touch sensor panel. An example of such a touch sensor panel is described in, for example, Applicant's U.S. Pat. No. 8,026,903 entitled “Double-Sided Touch Sensitive Panel and Flex Circuit Bonding,” issued on Sep. 27, 2011, the content of which is incorporated by reference herein. It should be understood that, as referred to in this document, a DITO touch sensor panel can use material other than ITO.
Another type of touch sensor panels can have co-planar single-layer touch sensors fabricated on a single side of a substrate. That is, the drive lines and sense lines forming the touch nodes can be formed on the same surface of a substrate. This type of touch sensor panels is referred to as Single-layer Indium Tin Oxide (SITO) touch sensor panel. An example of an SITO touch sensor panel is described in, for example, Applicant's U.S. Pat. No. 8,633,915 entitled “Single-Layer Touch-Sensitive Display,” issued on Jan. 21, 2014, the content of which is incorporated by reference herein. It should be understood that, as referred to in this document, a SITO touch sensor panel can use material other than ITO.
Touch sensor panels can be found in various electronic devices such as smartphones, tablets, and wearable devices and ideally need to be designed to conform to the various form factors of these devices while providing consistent touch sensitivity across the panel.